The studies detailed in this research plan are designed to prospectively investigate the magnitude and mechanism of the physiologic adaptations that occur when older patients with coronary heart disease (CHD) participate in a 3-month and a 12- month program of aerobic exercise conditioning. A control group will consist of nonexercising older CHD patients. Central to this project is the capacity of CHD patients, age 62 years and older, to adapt to an aerobic exercise program with an increase of maximal aerobic capacity as measured by maximal exercise oxygen consumption, and by an increase submaximal endurance capacity as measured by an exhaustive submaximal exercise protocol. Submaximal indices of conditioning, such as heart rate- blood pressure product and blood lactate concentration at a given workload, will also be emphasized as they are applicable to daily activities. Cardiac adaptations to training will include radionuclide ventriculographic indices of left ventricular performance, corrected for measures of ventricular loading conditions, as well as measures of submaximal and maximal exercise heart rat-blood pressure product, and index of myocardial oxygen demand. Peripheral adaptations to training will include measures of post-ischemic exercise calf blood flow and conductance and muscle biopsy sample for determination of capillarity and oxidative enzyme activity and glucose stores. Blood lactate determination during the exhaustive submaximal endurance protocol will assess adequacy of skeletal muscle oxygenation during exercise. Preliminary data from our laboratory suggests that older CHD patients obtain a similar relative training benefit as younger CHD patients yet are far less likely to participate in an organized cardiac conditioning program. Entry level data (clinical, demographic, psychosocial) will be analyzed to determine predictors of participation and nonparticipation in an exercise- based rehabilitation program for older coronary patients.